1. Field of the Invention:
The present invention relates to a process for effectively producing an olefin homopolymer or an olefin copolymer. The present invention also relates to a catalyst used for olefin polymerization.
2. Related Art:
Heretofore, the Kaminsky type catalysts containing a transition metal compound and aluminoxane have been known as a soluble olefin polymerization catalyst. For example, the following catalysts are known. In the alpha-olefin polymerization, a catalyst composed of a zirconium compound and aluminoxane shows high polymerization activity (Japanese Patent Application Unexamined Publication No. Sho 58-19309). Stereo-regular polypropylene is produced using a catalyst composed of a zirconium compound having a ligand in which two indenyl groups are connected through an ethylene group, and aluminoxane (JP Pat. Appln. Unexamined Pub. No. Sho 61-130314). It is said that using these Kaminskey type catalysts, for example, in the propylene polymerization, any of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene can be produced (Macromol. Chem., Rapid Commun. 4,417-421 (1983); Angew. Chem. Int. Ed. Engl. 24,507-508 (1985); J. Am. Chem. Soc. 109,6544-6545 (1987); and J. Am. Chem. Soc. 110,6255-6256 (1988)).
In this case, as a transition metal compound useful for producing isotactic polypropylene, a transition metal compound having an ethylene bis(indenyl) ligand (JP Pat. Appln. Unexamined Pub. No. Sho 61-264010; Sho 64-51408; and Sho 64-66216); R(C.sub.5 (R').sub.4).sub.2 MeQ.sub.p type metallocene compound reported by Ewen et al (JP Pat. Appln. Unexamined Pub. No. Sho 63-251405; Sho 63-295607; and Sho 64-74202); a metallocene compound cross-linked with silicon or the like (JP. Pat. Appln. Unexamined Pub. No. Hei 3-12406); and the like are known. Further, a metallocene compound useful for producing a stereo-block polymer is known (JP Pat. Appln. Unexamined Pub. No. Sho 63-142004 and Sho 63-2005).
However, the above-mentioned polymerization methods require use of a great amount of expensive aluminoxane to obtain sufficient activity, resulting in increase in cost.
Further, since a great amount of aluminoxane is used, a substantial amount of metal will remain in the polymerized products, resulting in deterioration and coloring of the products. In these processes, after polymerization, deashing treatment of the resultant products should be sufficiently conducted. Thus, these processes have a problem in productivity.
Further, aluminoxane is produced from the reaction of highly reactive trimethylaluminum and water, leading to risks. Furthermore, the reaction product is a mixture of several materials containing unreacted materials, and it is quite difficult to isolate one single substance. Thus, management of catalysts to obtain a product having stable physical properties is quite difficult.
On the other hand, Japanese Patent Application PCT Publication No. Hei 1-502036 discloses a polymerization process for producing an alpha-olefin polymer using, as a catalyst, a specific boron complex containing a specific amine and a metallocene compound.
However, the catalyst used in the above-mentioned process shows extremely low polymerization activity. Further, it is difficult to apply this process to industrial use since the resultant polymer is in the bad shape, leading to low bulk density.
Further, JP Pat. Appln. Unexamined Pub. No. Hei 03-74411 and Hei 03-74412 disclose olefin polymerization employing a catalyst wherein at least one of a transition metal compound and aluminoxane is carried on a carrier made of a granule polymer or an inorganic particle. However, these process require use of a great amount of aluminoxane, and thus are not suitable for industrial use for the same reasons.
Further, International Publication 91/09882 and JP. Pat. Appln. Unexamined Pub. No. Hei 03-234709 propose an olefin polymerization catalyst wherein a specific transition metal compound is carried on a carrier. However, in these catalysts, the catalyst components are limited and these are not always satisfactory for industrial use.